This invention relates in general to a precast concrete smokestack constructed by stacking sections axially one upon the other. In particular this invention relates to a sectional smokestack where each of the sections is assembled at the job site from multiple segments and further relates to the structure for tying these segments together to form an integral section.
Masonry stacks are well known where materials such as bricks are stacked and secured to one another with mortar. Concrete stacks are also known where the smokestack is constructed at the job site either by pouring the concrete stack directly or by constructing the stack with precast concrete sections.
For example, U.S. Pat. No. 4,104,868 describes a sectionalized precast concrete smokestack. This patent describes a method of contructing a chimney by stacking interfitting one-piece segments vertically to form an inner liner of a dual wall smokestack and then constructing an outer wall spaced from the inner liner by stacking interfitting one-piece segments vertically and in surrounding relation to the inner liner. Reinforcing steel bars are placed in the interstitial gap between the inner liner and the outer wall during construction of the stack and concrete is poured in situ into the gap to cement the adjacent segments together and to cement the inner wall to the outer wall. The outer wall includes circumferential reinforcing steel hoops to permit the outer wall to contain hoop stresses.
In these prior art concrete stacks constructed such as shown in U.S. Pat. No. 4,104,868 there is a practical limitation on the circumferential size of the stack to be constructed because of the limitations on the size of the inner liner one-piece segments and the outer wall one-piece segments. As the diameter of the stack becomes larger these segments become more unwieldy. Further, with only reinforcing hoops in the outer wall and no reinforcing rods in the inner liner there is a greater possibility of breakage or cracking of the segments during assembly.